1. Field of the Invention
The present invention relates to a method of manufacturing a liquid ejection head, and more particularly, to a method of manufacturing a piezoelectric type liquid ejection head.
2. Description of the Related Art
An image forming apparatus, such as an inkjet printer, is known which comprises a piezoelectric type print head (liquid ejection head) that ejects ink droplets from nozzles by applying pressure to ink accommodated in pressure chambers, through changing the volume of the pressure chambers by means of the displacement of piezoelectric elements.
In recent years, there have been demands for improved image quality in the images formed by image forming apparatuses of this kind. For this purpose, it is necessary further to reduce the size of the ink droplets ejected from the nozzles of the print head, and to increase the density of the nozzles (to achieve high integration), and consequently, the surface area (size) of each pressure chamber must be reduced. Moreover, in the print head based on the piezoelectric system in particular, it is necessary to form the piezoelectric bodies that constitute the piezoelectric elements as very thin films in order to obtain a desired displacement volume in small-sized pressure chambers.
There are known methods of forming piezoelectric bodies including a method using bulk material and a method using screen printing. In the method using bulk material, it is necessary to polish the bulk material in order to form the piezoelectric bodies as thin films; however, there are restrictions on handling and it is then difficult to form the bodies to a thickness of 30 μm or below. On the other hand, in the method using screen printing, it is possible to form the piezoelectric bodies to a thin dimension; however, if it is attempted to print piezoelectric bodies onto positions corresponding to pressure chambers, through a screen, then there is a problem in that processing of the film thickness of a plurality of piezoelectric bodies is difficult, due to droop of the edge portions, and the like.
Japanese Patent Application Publication No. 2003-69106 discloses a method in which lower electrodes are formed by means of screen printing, or the like, on a substrate at positions corresponding to pressure chambers on the substrate, a piezoelectric body (piezoelectric film) is then formed on the whole surface of the substrate in such a manner that the piezoelectric body covers the lower electrodes, a mask is then formed on the piezoelectric body by means of photolithography, the portions of the piezoelectric body not covered by the mask are then removed by means of sandblasting, individual piezoelectric bodies are thereby created, the structure is then calcined, and upper electrodes are then formed by means of screen printing, or the like, on the individual piezoelectric bodies.
Japanese Patent Application Publication No. 11-207970 discloses a method in which, lower electrodes, piezoelectric bodies and upper electrodes are formed in positions corresponding to pressure chambers on a substrate by a method similar to that disclosed in Japanese Patent Application Publication No. 2003-69106, the upper electrodes are then further divided into a plurality of electrodes by means of sandblasting, or the like, in such a manner that a plurality of pressurization devices are provided for each pressure chamber.
In Japanese Patent Application Publication Nos. 2003-69106 and 11-207970, however, the lower electrodes and the upper electrodes are formed individually by screen printing, or the like, at the positions on the substrate corresponding to the pressure chambers, whereas the piezoelectric body is first formed over the whole surface of the substrate and is then divided into individual piezoelectric bodies at the positions on the substrate corresponding to the pressure chambers, by means of photolithography and sandblasting. In other words, the lower and upper electrodes and the piezoelectric bodies are formed by different methods at the positions on the substrate corresponding to the pressure chambers, and hence the manufacturing process of the piezoelectric elements is complicated. Moreover, positional divergence between the lower electrodes, the piezoelectric bodies and the upper electrodes is liable to occur, and hence there is a risk of variations in the ejection performance, such as the volume and speed of flight, of the ink droplets ejected from the nozzles.
Furthermore, when the portions of the piezoelectric body not covered by the mask are removed by a sandblasting process, then the substrate on which the piezoelectric body is to be formed becomes the blast stopping surface, which receives and stops the blasted abrasive particles, and there is a risk that the substrate may be damaged and degraded by the abrasive particles.